Electrode member for retinal stimulation, and artificial retinal device using the electrode member

ABSTRACT

An object is to provide an electrode member for retina stimulation which can form an actually transmitted image without pressing the retina in an excessively broad range and to provide an artificial retina device using the electrode member. An electrode member includes electrodes disposed in a shape of a vertical and horizontal matrix, a support holding each electrode at a predetermined position, and a fixing pin fixing four corners of the support to a sclera. Each electrode projects in the shape of a needle from an opposed face of the support toward a retina. The fixing pin is provided with a positioning projection allowing a distal end of each electrode to come into contact with retinal bipolar cells and limiting the overall opposed face to come into contact with a retina when the support is fixed to the retina.

TECHNICAL FIELD

The present invention relates to an electrode member for retinalstimulation, and an artificial retina device or the like using theelectrode member.

DESCRIPTION OF BACKGROUND ART

No effective cure has yet been found for loss of sight in spite ofrecent development in medical technique. Loss of sight is not only amere obliteration of visual function but also it affects a patient'sspiritual life and social life. Accordingly, a technique for curing theloss of sight has been desired.

FIG. 1 is a sectional view of a retina. A sclera A forming an outerlayer of an eyeball is outside a retina. Inside the sclera arephotoreceptors B, retinal bipolar cells C and retinal ganglion cells Dsequentially in this order. Of these, the photoreceptors B serve toreceive light and convert it to an electric signal. The retinal bipolarcells C and retinal ganglion cells D serve to transmit the electricsignal to the brain. Light incident in front of the eyeball (fromdownward in the figure) passes through the transparent retinal ganglioncells D and retinal bipolar cells C to be sensed by the photoreceptors Band converted to an electric signal. Thereafter, the electric signal istransmitted through the retinal bipolar cells C to the retinal ganglioncells D. Distal ends of the retinal ganglion cells D extend into thebrain, and the electric signal forms an image in the brain.

FIG. 2 is a sectional view of a conventional electrode member forretinal stimulation 100 (hereinafter referred to as “electrode member100”) attached over a retina. The electrode member 100 is connected toone end of an electric wire 104 there to transmit, to the retinalbipolar cells C, an electric signal for an image transferred from theother end (not shown) of the electric wire. The electrode member 100 isprovided with a plurality of electrodes 101 transmitting an electricsignal, a support 102 holding the electrodes 101 at a predeterminedlocation (for example, in a matrix) and a fixing pin 103 for fixing thesupport 102 to the sclera A. Each electrode 101 is provided so as to beexposed flat on the underside (side in contact with the retina) of thesupport 102.

However, when the fixing pin 103 is inserted into the sclera A so thatthe electrode member 100 is fixed over the retina, the support 102 issometimes depressed against the retina more than necessary. In thiscase, since the electrode member 100 is fixed over the retina while theoverall underside of the support 102 is in contact with the retina,there is a possibility that the underside of the support may press theretina, adversely affecting the retina.

Furthermore, although a portion to which the electrode 101 originallysupplies the electric signal is the retinal bipolar cells C, theconventional electrode member 100 has such a structure that the electricsignal is also supplied to the retinal ganglion cells D as well. Theretinal ganglion cells D extend into the shape of a stalk in order totransmit electric signals from a plurality of the retinal bipolar cellsC. Accordingly, for example, as shown in FIG. 3, even when voltagecorresponding to an image of character “H” (voltage is applied to theelectrodes 101 indicated by “+”) is applied in the case of the electrodemember 100 provided with 36 electrodes 101, the user (a sightlessperson) sometimes recognizes it as an image of character “U.”

The present invention was made in view of the foregoing circumstances,and an object thereof is to provide an electrode member for retinalstimulation which can form an actually transmitted image withoutpressing the retina in an excessively broad range.

Furthermore, another object is to provide an artificial retina devicewhich can transmit an image signal into the brain using the electrodemember.

DISCLOSURE OF THE INVENTION

To solve the above-noted problem, a first invention is an electrodemember for retinal stimulation, provided with a plurality of electrodestransmitting electric signals to a retina and a support holding theelectrodes at predetermined positions, characterized in that the supporthas an opposed face opposed to the retina and provided with apositioning projection.

The retina means a sensory nerve epithelium located at an innermost ofthe eyeball and includes photoreceptors, retinal bipolar cells andretinal ganglion cells throughout the specification.

The positioning projection is provided so as to project from the opposedface of the support toward the retina side throughout the specification.Furthermore, a position where the positioning projection is provided isnot necessarily located inside the support and may be provided at aposition projecting at one side of the support. Furthermore, the numberof the positioning projections may be one or more. Furthermore, aplurality of electrodes may be disposed only in the center of thesupport and the other portion of the support may serve as thepositioning projection.

According to the first invention, the positioning projection of thesupport comes into contact with the retina when the electrode member forretinal stimulation is attached over the retina. Consequently, theeffect of press against a part of the retina stimulated by the electrodecan be reduced as compared with the case where the overall underside ofthe support comes into contact with the retina as in the prior art.

A second invention is characterized in that in the electrode member forretinal stimulation of the first invention, the positioning projectionadditionally serves as a fixing portion fixing the support onto theretina.

A shape of the electrode does not matter in the first and secondinventions, and for example, it may be a conventional sheet electrodecoming into contact with the retinal ganglion cells or a needle-shapedelectrode.

Throughout the specification, the fixing portion means a part fixing thesupport of the electrode member for retinal stimulation at apredetermined position on the retina and includes (a) one provided onthe support to give fixation due to attraction between the support andthe retina, or (b) one discrete from the support to press the supportagainst the retina thereby to fix the electrode member. As theconstruction included in (a) are exemplified a pin reaching the sclera,adhesive agent, thread joining by stitching the support and the retinaor the like. As the construction included in (b) is exemplified a memberpressing a front hemisphere within an eyeball thereby to fix thesupport.

“Additionally serving” includes, for example, (1) the case where thephysically identical construction serves both as the positioningprojection and the fixing portion, such as fixing a distal end of thepositioning projection (a face contacting with the retina) to theretinal using an adhesive agent or thread, and (2) the case where a partof the fixing portion serves as a positioning projection, for example, aproximal end of the pin serving as the fixing portion is formed with astepped portion so as to be thickened so that the stepped portion servesas a positioning projection coming into contact with the retina.

According to the second invention, since a single construction servesboth as the positioning projection and as the fixing portion, theconstruction of the electrode member for retinal stimulation can besimplified as compared with the case where both are provided so as toproject individually.

A third invention is an electrode member for retinal stimulation,provided with a plurality of electrodes transmitting electric signals toa retina and a support holding the electrodes at predeterminedpositions, characterized in that each electrode projects from an opposedface of the support opposed to the retina into a shape of a needle witha height reaching a retinal ganglionic layers of the retina.

Each electrode necessitates at least such a height as to reach theretinal bipolar cells from the surface side of the retina (the side ofthe retinal ganglion cells). Since the height is expected to differ fromone sightless person to another, the height is preferably measuredpreviously for each actual patient. Thus, the height of each electrodecannot be defined unconditionally, but generally ranges from about 100μm to about 300 μm.

According to the third invention, each electrode supplying the electricsignal is formed into the needle shape with a predetermined height andthe electrode member is attached to the retina so that each electrode isbrought into direct contact with the retinal bipolar cells. Accordingly,an image more approximated to an actual one can be formed as comparedwith the conventional case where the electric signal is applied via theretinal ganglion cells to the retinal bipolar cells.

A fourth invention is characterized in that in the electrode member forretinal stimulation of the first or second invention, each electrodeprojects from an opposed face of the support opposed to the retina intoa shape of a needle with a height reaching a retinal ganglionic layersof the retina.

According to the fourth invention, an adverse effect of pressing theretina can be reduced since the positioning projection is provided.Furthermore, an image more approximate to an actual one can be formedsince the needle-shaped electrodes transmit the electric signalsdirectly to the retinal bipolar cells.

A fifth invention is characterized in that in the invention of each ofclaims 3 and 4, each electrode is covered with an insulator in anoverall periphery except a distal end thereof.

The phrase, “except a distal end thereof” means that the electrodemember is arranged so that the electric signal each electrode appliesstimulates only the targeted retinal bipolar cells and does notstimulate other cells.

According to the fifth invention, an image more approximate to an actualone can be formed since the electric signal tends to be applied only tothe retinal bipolar cells.

A sixth invention is characterized in that in the invention of each ofclaims 3 to 5, the opposed face of the support is provided with a groundelectrode.

The ground electrode may be provided on a part of the opposed face ofthe support or the overall opposed face of the support.

When a sheet electrode is provided on the opposed face of the support, aground electrode cannot be brought into contact with the retina and isaccordingly provided on a portion different from an eyeball. Accordingto the sixth invention, however, the ground electrode can be provided soas to be in contact with the retina since the electrode is formed intothe needle shape and inserted into the retina.

A seventh invention is a method of retinal stimulation, characterized byapplying a first stimulating voltage to electrodes corresponding to apredetermined image pattern among a plurality of electrodes for retinalstimulation disposed in a matrix shape, and applying a secondstimulating voltage to electrodes corresponding to a background regionof the image pattern, the second stimulating voltage having a reversedpolarity to the first stimulating voltage relative to a ground polarity.

An eighth invention is an artificial retina device characterized by theelectrode member for retinal stimulation described in any one of claims1 to 6, a fixing portion fixing the electrode member onto a retina and asignal transmission section transmitting an image forming electricsignal to the electrode.

The signal transmission section transmits an electric signal to anelectrode. The signal transmission section can be provided outside theeyeball and connected to an electric wire extending from the electrode.However, the signal transmission section is preferably providedintegrally with the electrode member for retinal stimulation andimplanted in the eyeball. In this case, a signal transmitting circuit ispreferably provided on an outer body of the user so that the electricsignal is transmitted by a wireless system (for example, electric wave,optical signal).

According to the eighth invention, the electric signal transferred fromthe signal transmission section is transmitted via the electrode to theretinal ganglion cells to be formed into an image within the brain.

A ninth invention is an artificial retina device comprising an electrodemember for retinal stimulation, provided with a plurality of electrodestransmitting electric signals to a retina and a support holding theelectrodes at predetermined positions, a fixing portion fixing theelectrode member onto the retina and a signal transmission sectiontransmitting an image forming electric signal to the electrode,characterized in that said plurality of the electrodes are disposed in amatrix shape, a first stimulating voltage is applied to the electrodescorresponding to a predetermined image pattern among said plurality ofthe electrodes, and a second stimulating voltage is applied to theelectrodes corresponding to a background region of the image pattern,the second stimulating voltage having a reversed polarity to the firststimulating voltage relative to a ground polarity.

Furthermore, a tenth invention is an artificial retina device comprisingthe electrode member for retinal stimulation described in any one ofclaims 1 to 6, a fixing portion fixing the electrode member onto aretina and a signal transmission section transmitting an image formingelectric signal to the electrode, characterized in that said pluralityof the electrodes are disposed in a matrix shape, a first stimulatingvoltage is applied to the electrodes corresponding to a predeterminedimage pattern among said plurality of the electrodes, and a secondstimulating voltage is applied to the electrodes corresponding to abackground region of the image pattern, the second stimulating voltagehaving a reversed polarity to the first stimulating voltage relative toa ground polarity.

It is known that a retinal bipolar cell includes an ON-type whichtransmits positive voltage pulses to retinal ganglion cells in responseto light stimulus to the photoreceptor and an OFF-type which transmitsnegative voltage pulses to retinal ganglion cells. In conventionalartificial retina devices, a stimulating voltage is applied to only oneor more of a plurality of electrodes corresponding to an image pattern.Accordingly, it is difficult to achieve a sufficient contrast withrespect to the image pattern.

In each of the seventh, ninth and tenth inventions, the first and secondstimulating voltages are applied in view of the ON-type and OFF-typebipolar cells. The first stimulating voltage corresponds to an imagepattern and the second stimulating voltage corresponds to a backgroundregion of the image pattern and has a reversed polarity to the firststimulating voltage relative to a ground polarity. Consequently, asufficient contrast can be given to the image pattern formed in thebrain.

An eleventh invention is characterized in that in the tenth invention, acontrol device is provided for controlling the image forming electricsignal, and the fixing portion serves as a coil capable of supplying apower source to the control device.

When the signal transmission section and the electrode member areattached in the eyeball, it is preferable to transmit a signal fromoutside the eyeball to the signal transmission section by radiotransmission. In such an arrangement, a control device (for example, amicrocomputer) controlling the electric signal is preferably providedbetween the signal transmission section and the electrode member. Inthis case, however, it is difficult to supply electric power to thecontrol device. Accordingly, the fixing portion is arranged to alsoserve as a coil in the present invention so that an induction current isinduced in the coil, whereby electric power can be supplied to thecontrol device.

A twelfth invention is an operating method characterized by forming anopening by opening a front of an eyeball and inserting an artificialretina device into an inside of the eyeball. Furthermore, the artificialretina device is preferably described in any one of claims 8 to 11.

Tissues (for example, cornea) in the front of the eyeball are notnecessarily left for a person undergoing an operation for implanting inan eyeball the artificial retina device described in each of the eighthto eleventh inventions. Accordingly, the front of the eyeball can beopened so that an opening is formed. In this surgical manner, theartificial retina device can easily be inserted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a retina;

FIG. 2 is a side sectional view of a retina to which a conventionalexample of electrode member for retinal stimulation is attached;

FIG. 3 illustrates a manner of applying a stimulating voltage to aplurality of electrodes in the conventional example;

FIG. 4 is a side sectional view of a retina to which a first embodimentof electrode member for retinal stimulation is attached;

FIG. 5 is an enlarged side sectional view of the retina to which thefirst embodiment of electrode member for retinal stimulation isattached;

FIG. 6 is a diagram of an artificial retina device of the firstembodiment;

FIG. 7 illustrates a manner of applying a stimulating voltage to aplurality of electrodes in the first embodiment;

FIG. 8 is a timing chart showing a first stimulating voltage (A) and asecond stimulating voltage (B) both applied to a plurality of electrodesin the first embodiment;

FIG. 9 is a side sectional view of the artificial retina device attachedin the eyeball in a second embodiment;

FIG. 10 illustrates a front of the eyeball, showing a degree of incisionin the case where the artificial retina device of the second embodimenthas been attached in the eyeball;

FIG. 11 is a diagram of the artificial retina device of the secondembodiment;

FIG. 12 is a side sectional view of the artificial retina deviceattached in the eyeball in a third embodiment;

FIG. 13 illustrates a front of the eyeball, showing a degree of incisionin the case where the artificial retina device of the third embodimenthas been attached in the eyeball;

FIG. 14 is a diagram of the artificial retina device of the thirdembodiment;

FIG. 15 illustrates appearances of the artificial retina device of thethird embodiment having been attached in the eyeball, (A) being a frontview, (B) a side view and (C) a rear view; and

FIG. 16 is a side view of the artificial retina device of the thirdembodiment before attachment in the eyeball.

In the figures, 1 . . . electrode member for retinal stimulation, 2 . .. electrode, 3 . . . support, 3A . . . opposed face, 4, 23 . . . fixingportion, 5 . . . positioning projection, 6 . . . ground electrode, 7,11, 21 . . . signal transmission section, 22 . . . control device, 8,10, 20 . . . artificial retina device, C . . . retina bipolar cell, andF . . . retina.

BEST MODE FOR ENFORCING THE INVENTION

Several embodiments of the present invention will be described withreference to the accompanying drawings. However, the technical scope ofthe invention should not be limited by the following description of theembodiments but may be modified without departing the gist. Furthermore,the technical scope of the present invention should cover a scope ofequivalence.

First Embodiment

A first embodiment will be described with reference to FIGS. 1 to 8.FIG. 1 is a side sectional view of a retina F of a healthy person. Thesclera A is located outside the retina F and covers an outer face of theeyeball. Inside the sclera A are photoreceptors B, retinal bipolar cellsC and retinal ganglion cells D sequentially in this order. The electrodemember 1 for retinal stimulation of the embodiment (hereinafter referredto as “electrode member 1”) is expected to be applied to patients ofRetinitis Pigmentosa and age-related macular degeneration (ARMD). Insymptoms of these patients, photoreceptors B are degenerated such thatlight cannot be converted to electric signals. Next, a visual path suchas the retinal bipolar cells C and retinal ganglion cells D fails tofunction, which failure results in loss of sight. However, it is knownthat about 70% of the retinal bipolar cells C and about 30% of theretinal ganglion cells D are left in a patient heavily suffered fromRetinitis Pigmentosa. The electrode member 1 is mounted at the retinalganglion cells D side to directly transmit electric signals to retinalbipolar cells C.

The description will go forward with reference to FIGS. 4 to 7. FIG. 4shows the electrode member 1 attached to the retina. The electrodemember 1 comprises a plurality of electrodes 2 transmitting electricsignals to the retina F, a support 3 holding the electrodes 2 in a shapeof a vertical and horizontal matrix, and a fixing pin 4 (correspondingto a fixing portion in the invention) fixing the support 3 to theretina. The support 3 is made of an insulating resin (for example,Kepton manufactured by CHOMERICS CO.) into the shape of a generallyrectangular thin plate. As shown in an enlarged form in FIG. 5,electrodes 2 are disposed at respective predetermined positions insidethe support 3. Each electrode 2 (which can be made from iridium, forexample) projects in the shape of a needle from an opposed face 3A ofthe support 3 opposed to the retina F (lower in FIG. 5). Each electrode2 has a height L starting from the opposed face 3A and set to extendfrom the surface E of the retina to the retinal bipolar cells C.Furthermore, each electrode 2 is covered with an insulating resin overits entire periphery except for its distal end 2A.

Four corners of the support 3 are provided with respective fixing pins 4having distal ends 4B projecting from the opposed face 3A. Each fixingpin 4 is made from a ceramic, for example, and has a rear end pressingportion 4A projecting at a top 3B side of the support 3. Each pressingportion 4A is formed into the shape of a disc and pressed when thedistal end 4B side of the fixing pin 4 is forced into the sclera A. Eachfixing pin 4 has a positioning projection 5 fitted with the distal end4B side thereof.

Each positioning projection 5 is made from a synthetic resin and formedinto a generally cylindrical shape and has an inner diameter slightlysmaller than an outer diameter of each fixing pin 4. Each positioningprojection 5 has one side bonded to the opposed face 3A. Eachpositioning projection 5 has a height M which is set to be larger thanthe height L of each electrode 2 by a predetermined length (as will bedescribed in detail later). A total area of four lower end faces 5A(brought into contact with the retina F) of the positioning projections5 is set to be smaller than an area of the opposed face 3A.

A ground electrode 6 is provided on the parts of the opposed face 3Awhere no electrodes 2 project, as shown in FIG. 5. The ground electrode6 is formed as a continuous body and is attached integrally to theopposed face 3 side.

In order that the electrode member 1 may be attached to the retina, theoverall electrode member 1 is disposed at the predetermined positionwhile the opposed face 3A of the support 3 is being opposed to theretina F. Subsequently, the distal end 4B of the fixing pin 4 isinserted into the retina F, and the pressing portion 4A is furtherpressed so that the distal end 4B is forced into the sclera A. In thiscase, the forcing operation progresses while the retina F is sandwichedbetween the lower end face 5A of the positioning projections 5 and thesclera A. Since the sclera A has a certain strength, it pushes the lowerend face 5A back (via the sandwiched retina F) when the pressing portion4A is pressed to a predetermined depth. Consequently, the fixing pin 4is found to have been thrust into a predetermined depth. Thus, the lowerend face 5A of the positioning projection 5 is positioned. When theelectrode member 1 is attached at a predetermined position, thedifference (M−L) between the height M of the positioning projection 5and the height L of the electrode 2 brings the distal ends 2A of theelectrodes 2 into contact with the retinal bipolar cells C through theretinal ganglion cells D. Thus, after the electrode member 1 has beenattached, electric signals corresponding to an image pattern aretransmitted via the electrodes 2 to the retinal bipolar cells C, wherebyimages can be sent into the brain of the user. As shown in FIG. 6, asignal circuit 7 (corresponding to a signal transmission section in thepresent invention) is connected via electric wires W extending from theelectrodes 2 to the electrode member 1 which is to be attached to theretina in the eyeball. An artificial retina device 8 comprising thesignal circuit 7 and the electrode member 1 is attached to the user (orsightless person). The signal circuit 7 is arranged to transmit apredetermined electric signal corresponding to an image to a pluralityof electrodes 2. The electric signal is transmitted through the distalend 2A of the electrode 2 to the retinal bipolar cells C.

A manner of processing the electric signals the signal circuit 7supplies to a plurality of the electrodes 2 (method of stimulatingretina) will be described with reference to FIGS. 7 and 8. FIG. 7 showsthe electrode member 1 provided with thirty-six electrodes 2 arranged inthe matrix of 6×6. For example, when a generally cross-shaped imagepattern is to be transmitted, a first stimulating voltage (FIG. 8A) isapplied to the electrodes designated by “+” (or the electrodescorresponding to the cross-shaped image pattern). Furthermore, a secondstimulating voltage (FIG. 8B) is applied to the electrodes correspondingto a background region of the cross-shaped image pattern (designated by“−”), the second stimulating voltage having a reverse polarity relativeto the ground electrode or first stimulating voltage. Thus, the contrastof image can be improved since the stimulating voltages of bothpolarities are applied to the electrodes.

According to the embodiment, the positioning projections 5 have thetotal area brought into contact with the retina F and set to be smallerthan the area of the opposed face 3A of the support 3. When theelectrode member 1 is attached to the retina, the positioningprojections 5 are brought into contact with the retina F. Accordingly,effect of pressure against the retina F can be reduced as compared withthe case where the overall underside of the support 102 is brought intocontact with the retina F as in the prior art.

Furthermore, each positioning projection 5 also serves as each fixingpin 4. Accordingly, the arrangement of the electrode member 1 can besimplified as compared with a case where each positioning projection andeach fixing pin project individually. Additionally, since each fixingpin 4 is brought into contact with the retina F, each fixing pin 4 tendsto be subjected to stress. Accordingly, when each positioning projection5 and each fixing pin 4 are combined together, a part which is mostliable to be suffered to stress is fixed, whereupon the overallelectrode member 1 can be positioned readily.

Furthermore, each electrode 2 supplying an electric signal is formedinto the needle shape and has the predetermined height and is attachedto the retina so as to be brought into direct contact with the retinalbipolar cells. Consequently, an image more approximated to an actual onecan be formed as compared with the case where the electric signal isapplied via the retinal ganglion cells to the retinal bipolar cells asin the conventional electrode 101.

Furthermore, each electrode 2 is covered with the insulator in anoverall periphery except a distal end 2A thereof. Consequently, sincethe electric signal tends to be supplied only to a target, an image moreapproximated to an actual one can be formed.

Furthermore, since each electrode 2 is formed into the needle shape andinserted into the retina, the ground electrode 6 can be provided so asto be brought into contact with the retina.

Furthermore, in view of the fact that the retinal bipolar cell includestwo types of cells, ON-type and OFF-type, the first and secondstimulating voltages corresponding to the image pattern and thebackground region of the image pattern are applied to a plurality of theelectrodes 2, the second voltage having a reversed polarity relative tothe ground electrode. Consequently, a sufficient contrast can be appliedto the image pattern formed in the brain. Furthermore, as a secondaryeffect, when an image pattern with the same contrast as in the prior artis transmitted (even when an image pattern with finer contrast than inthe prior art depending on conditions is transmitted), small current isrequired such that electrical damage the retina F suffers can bereduced.

Second Embodiment

A second embodiment will be described with reference to FIGS. 9 to 11.Firstly, the arrangement of the second embodiment will be described withreference to FIG. 11. The artificial retina device 10 comprises theelectrode member 1 and the signal transmitting section 11. Both members1 and 11 are connected to each other by the electric wire W. Theartificial retina device 10 is designed to be attached to an inner partof the eyeball G. The signal transmitting section 11 is a receiver whichreceives image-forming electric signals from a transmitter 12 providedoutside the eyeball G, by a radio system. The signal transmittingsection 11 has an outer diameter which ranges from about 5 mm to about 8mm and is substantially as large as or slightly larger than an innerdiameter of a crystal lens H. A signal control device 13 (including forexample, a CCD camera, microcomputer, etc.) is connected to thetransmitter 12 for generating and controlling image signals.

In order that the artificial retina device 10 may be attached to theinner part of the eyeball G, the front of the eyeball is cut along anouter periphery of the crystal lens H so that an opening J is formed, asshown in FIG. 10. The electrode member 11 and the signal transmittingsection 11 are in turn attached through the opening J into the innerpart of the eyeball G.

According to the embodiment, the electric signals from the signaltransmitting section 11 are transmitted via the electrodes 2 to theretinal ganglion cells D of the retina F, whereupon an image is formedin the brain.

Third Embodiment

A third embodiment will be described with reference to FIGS. 12 to 16.Firstly, the arrangement of the second embodiment will be described withreference to FIG. 14. The artificial retina device 20 comprises theelectrode member 1, the signal transmitting section 21 transmittingelectric signals to the electrode member 1, a control device 22(including a microcomputer) controlling the electric signals and afixing section 23. The signal transmitting section 21 is a receiverwhich receives image-forming electric signals from a transmitter 24provided outside the eyeball G, by a radio system. The control device 22includes a control circuit 25 and a power supply device 26. The powersupply device 26 is a secondary cell such as a lithium cell. The fixingsection 23 is provided for fixing the electrode member 1 to the retina(the construction thereof will be described in detail later). The fixingsection 23 also serves as a coil to supply to the power supply device 26a power supply fed by electromagnetic induction from an external primarycoil 27. A signal control device 29 (including for example, a CCDcamera, microcomputer, etc.) is connected to the transmitter 24 forgenerating and controlling image signals. The signal control device 29further controls the primary coil 27.

The electrode member 1, signal transmitting section 21 and controldevice 22 are formed integrally into a generally circularly cylindricalbody 28 as shown in FIGS. 15 and 16. The cylindrical body 28 is sized soas to be accommodated in the eyeball G as shown in FIG. 14. Morespecifically, the cylindrical body 28 has a length substantially equalto a length from a yellow spot or retinal fovea to an iris back. Thecylindrical body 28 has, at a front of the eyeball Ganouter, diameterslightly smaller than a diameter of a boundary between the sclera and acornea.

Furthermore, four fixing sections 23 are disposed substantiallyuniformly along an outer periphery of a front half (a portion located ata front semispherical portion in the eyeball G; and inner face ofciliary body) of the cylindrical body 28. The fixing sections 23 projectoutward. Each fixing section 23 comprises a member having a suitableresiliency (for example, a shape memory alloy). Both edges of eachfixing section 23 are connected to an outer face of the cylindrical body28 so as to be formed into the shape of a bridge. Each fixing section 23has a front 23A formed into an arc shape in compliance with an innerwall of the eyeball G. The fixing section 23 is folded along the outerface of the cylindrical body 28 before the artificial retina device 20is attached inside the eyeball G. On the other hand, after theartificial retina device 20 has been attached inside the eyeball G, thefixing section 23 projects radially with respect to the cylindrical body28 and is in contact with an inner wall of the front semisphericalportion of the eyeball G, as shown in FIGS. 12 and 15. Thus, the fixingsection 23 presses the cylindrical body 28 rearward in the eyeball G sothat the support 3 of the electrode member 1 is pressed toward theretina F side, whereby the support is fixed at a predetermined positionon the retina.

In order that the artificial retina device 20 constructed as describedabove may be attached inside the eyeball G, the front of the eyeball isopened so that an opening K is formed, as shown in FIG. 13. Theartificial retina device 20 is inserted through the opening K into theinner part of the eyeball G. In a surgical operation for implanting theartificial retina device 20 in the eyeball G, a portion of the eyeball Gin the rear of the inner wall portion with which the fixing section 23is in contact is preferably processed by laser along the innerperipheral face. Even if the fixing section 23 should cause a retinaldetachment, it can be arrested from progress toward the retinal fovea asthe result of such processing of laser solidification.

According to the embodiment, the fixing section 23 serves as the coil,and the induction current is generated in the coil, whereupon a powersupply can be provided for the control device 22.

Furthermore, the artificial retina device can be inserted easily byemploying the surgical operation for opening the front of the eyeball G.

The fixing section 23 serves as the coil in the embodiment. However, thefixing section may also serve as an earth, as another modified form.Furthermore, since the fixing section 23 positions the support 3 in theembodiment, the fixing pin 4 for the electrode need not be provided.

1. An electrode member for retinal stimulation comprising: a pluralityof electrodes transmitting electric signals to a retina; a supportholding the electrodes at predetermined positions, the support having anopposed face opposed to the retina, each electrode projecting from theopposed face of the support into a shape of a needle that tapers into asharp point with a height reaching retinal ganglionic layers of theretina; and positioning projections, each having first and secondsurfaces, the first surface being attached to the opposed face of thesupport, the second surface located a distance beyond the height of theelectrodes, each positioning projection having a fixing pin locatedtherein extending beyond the second surface of the positioningprojections.
 2. An electrode member for retinal stimulation according toclaim 1, wherein the positioning projection additionally serves as afixing portion fixing the support onto the retina.
 3. An electrodemember for retinal stimulation according to claim 1, wherein eachelectrode is covered with an insulator in an overall periphery except adistal end thereof.
 4. An electrode member for retinal stimulationaccording to claim 1, wherein the opposed face of the support isprovided with a ground electrode.
 5. An artificial retina devicecomprising the electrode member for retinal stimulation according toclaim 4, said device further comprising a signal transmission sectiontransmitting an image forming electric signal to the electrode.
 6. Anoperating method characterized by forming an opening in a front of aneyeball and inserting the artificial retina device of claim 5 into aninside of the eyeball.
 7. An artificial retina device comprising theelectrode member for retinal stimulation according to claim 1, saiddevice further comprising a signal transmission section transmitting animage forming electric signal to the electrodes, wherein: said pluralityof electrodes are disposed in a matrix shape; a first stimulatingvoltage is applied to electrodes corresponding to a predetermined imagepattern among said plurality of electrodes; and a second stimulatingvoltage is applied to electrodes corresponding to a background region ofthe image pattern, the second stimulating voltage having a reversedpolarity to the first stimulating voltage relative to a ground polarity.8. An artificial retina device according to claim 7, further comprisinga control device controlling the image forming electric signal, whereinthe fixing portion serves as a coil capable of supplying a power sourceto the control device.
 9. An operating method characterized by formingan opening in a front of an eyeball and inserting the artificial retinadevice of claim 8 into an inside of the eyeball.
 10. An operating methodcharacterized by forming an opening in a front of an eyeball andinserting the artificial retina device of claim 7 into an inside of theeyeball.
 11. A method of retinal stimulation, comprising the steps of:providing a support holding a plurality of electrodes at predeterminedpositions, each electrode projecting from an opposed face of the supportinto a shape of a needle that tapers into a sharp point with a heightreaching ganglionic layers of the retina; providing positioningprojections on the opposed face of the support, each positioningprojection having first and second surfaces, the first surface beingattached to the opposed face of the support, the second surface locateda distance beyond the height of the electrodes, each positioningprojection having a fixing pin located therein extending beyond thesecond surface of the positioning projections; applying a firststimulating voltage to electrodes corresponding to a predetermined imagepattern among the plurality of electrodes for retinal stimulationdisposed in a matrix shape; and applying a second stimulating voltage toelectrodes corresponding to a background region of the image pattern,the second stimulating voltage having a reversed polarity to the firststimulating voltage relative to a ground polarity.
 12. An artificialretina device comprising an electrode member for retinal stimulation,said electrode member comprising: a plurality of electrodes transmittingelectric signals to a retina, each electrode projecting from a supportholding the electrodes at predetermined positions and tapering into asharp point with a height reaching ganglionic layers of the retina;positioning projections, each having first and second surfaces, thefirst surface being attached to the opposed face of the support, thesecond surface located a distance beyond the height of the electrodes,each positioning projection havin a fixing pin located therein extendingbeyond the second surface of the positioning projections; and a signaltransmission section transmitting an image forming electric signal tothe electrodes, wherein: said plurality of electrodes are disposed in amatrix shape; a first stimulating voltage is applied to electrodescorresponding to a predetermined image pattern among said plurality ofelectrodes; and a second stimulating voltage is applied to electrodescorresponding to a background region of the image pattern, the secondstimulating voltage having a reversed polarity to the first stimulatingvoltage relative to a ground polarity.
 13. An operating methodcharacterized by forming an opening in a front of an eyeball andinserting the artificial retina device of claim 12 into an inside of theeyeball.